Cystic fibrosis (CF) is a genetic illness which has as its clinical features chronic pulmonary disease, pancreatic dysfunction and a high concentration of sodium and chloride in the sweat. Mucous plugs the pancreatic ducts, the intestinal mucous glands and the bronchial tree.
Studies have demonstrated raised levels of protein, predominately albumin, in meconium from infants with CF [See: Pediatrics, 21:635-641 (1958)]. A test device for the detection of albumin in meconium greater than 20 milligrams per gram (mg/g) dry weight of meconium has been developed. [See Pediatrics, 55:35-38 (1975)]. Such test devices suffer from a failure to detect all newborns with CF, i.e. low sensitivity, and an unacceptable number of false-positives, i.e., low specificity. Because of the emotional stress caused by a false-positive test result for CF, reduction in the number of false-positive test results in a CF test is desirable.
Pediatrics, 56:782-787 (1975) reported an increase in disaccharidase activities in meconium from infants with CF and suggested measurement of lactase activity as well as the other activities, as a CF diagnostic test. Am. J. Dis. Child., 132: 1112-1114 (1978) describes a study which included an assay test for lactase and .beta.-D-fucosidase activity in conjunction with an assay for albumin, in meconium. The authors suggest that the addition of the lactase and fucosidase assay would reduce the occurrence of false-positive test results.
The lactase activity test described above involved a liquid assay test. The meconium sample was placed in a test tube and a 3 percent lactose solution in a maleate buffer added. After incubation for a period of 15 minutes, lactase activity was detected by the presence of glucose, demonstrated by immersing a glucose reagent strip into the mixture and after 10 minutes, examining the glucose reagent strip for a blue color (positive test).
Use of a liquid assay test system for lactase activity detection in meconium samples is inconvenient. Because the meconium sample is a tarry-like mass, the sample must be first homogenized. As described in Am. J. Dis. Child., supra, the sample is homogenized with vigorous agitation in a buffer solution. Other workers have resorted to ultrasonic techniques to obtain homogenization. In order to properly prepare the sample for testing, the sample must be incubated for a period of from 15 minutes to one hour. In addition, the liquid assay test system requires the preparation of solutions for individual tests. In order to encourage greater screening for CF in infants, a more convenient test system is required, preferably a dip-and-read reagent strip. The present invention is directed to such a dip-and-read test device.